1. Field of the Invention
The present invention relates to improved coating, adhesive, sealant and elastomer (CASE) materials utilizing polymer latexes derived from various monomers and ethylenically unsaturated amine salts of sulfonic, phosphoric and/or carboxylic acids. More specifically, the invention relates to improved CASE materials produced using emulsion polymerization processes which utilize ethylenically unsaturated amine salts of alkylbenzene sulfonic acids, alkyl olefin sulfonic acids, alkyl alcohol sulfuric acid esters, or alkoxylated alkyl alcohol sulfuric acid esters, fatty acids, and fatty phosphate acid esters, or mixtures thereof.
2. Description of the Related Art
The emulsion polymerization of ethylenically unsaturated monomers to form discrete solid polymeric particles for use in coating, adhesive, sealant, and/or elastomer (CASE) applications is well known to the art. Surfactants are commonly used materials in the manufacture of various CASE products, such as, for example paints, printing inks, adhesives and pressure-sensitive adhesives. These surfactants are often indispensable for the manufacture and/or stabilization of these products in terms of processability. However, after such CASE products are used for coating, printing, adhesion or pressure bonding, the surfactants are no longer necessary, nor desirable, because surfactant remaining in the CASE product tends to adversely affect the resistance of the CASE material to water and even oil in many instances.
Surfactants for use in emulsion polymerization to form latexes, which are then used to prepare CASE materials, include traditional anionic surfactants, such as sodium dodecylbenzenesulfonate, and nonionic surfactants such as polyoxyethylene nonylphenyl ether. However, films of CASE materials using polymer latex emulsions prepared using such surfactants have the drawbacks of poor resistance to water and poor bond strength, typically because the surfactant remains in free form in the polymer latex film and/or final CASE material.
CASE materials typically comprise, for example, paints (high-gloss, semi-gloss, and flat), caulks, and the like. CASE materials are typically applied to a variety of substrates, including for example, wood, metal, plastic, glass, ceramics, fiberglass, composite materials, cardboard, corrugated board, paper, textiles, non-woven materials, foam, tape or a combination thereof. Substrates can be virgin materials, i.e. materials that have not previously been treated or coated with a case material, or materials that have been previously coated or treated with a CASE material. Namely, the CASE materials of the instant invention can be applied on top of or applied to a previously applied CASE material.
Conventional emulsion polymerization of ethylenically unsaturated monomers employs one or more water-soluble surfactants to emulsify the monomers and stabilize the resulting polymer products, i.e., the latex. The monomers used in emulsion polymerization reactions are generally water-insoluble, but in some cases may be water-soluble. During a typical emulsion polymerization, a surfactant is used to suspend small portions of monomer in a continuous or semi-continuous aqueous phase. Typically, the monomer molecules are suspended as small spheres in the aqueous phase, and the polymerization takes place within the small spheres. The water-soluble surface active agents, i.e., surfactants, typically utilized in emulsion polymerization reactions are anionic, nonionic, and cationic surfactants or mixtures thereof.
The polymeric particles formed by the emulsion polymerization process are typically utilized to prepare coating, adhesive, sealant, and/or elastomer (CASE) materials. In a traditional emulsion polymerization reaction, the surfactant does not chemically bond to the polymeric particles by carbon-carbon bond formation, but rather remains in the polymeric particle product solution after the emulsion polymerization reaction is complete, i.e., after all monomer is reacted. Unreacted surfactant can detrimentally affect a polymer product solution and/or film, because unreacted surfactant can interfere with the performance of such polymerization products in CASE materials, potentially causing the suspension of polymeric particles to become destabilized over time and undergo unwanted coagulation. Unreacted surfactant may cause unwanted peeling of a latex paint coating on a substrate, and decreased moisture and scrub resistance in other various CASE applications. Residual surfactant can cause an undesirable “blooming” that leads to surface irregularities in a resulting CASE material that is applied to a substrate. Additionally, residual surfactant may lead to undesirable decreases in adhesion of a particular CASE material. The traditional surfactants act as colloidal stabilizers before, during, and after polymerization, but they typically have a detrimental effect on the properties of a dry latex film, for example, due to their tendency to migrate, i.e., to leave their original positions at the latex particle surfaces and form areas of higher concentration pockets both within the film and at the film/air and film/substrate interfaces.
Several proposals have been made in the prior art to employ a polymerizable surface active agent during an emulsion polymerization reaction. U.S. Pat. No. 5,478,883 (incorporated herein by reference in its entirety) describes the use of ethylenically unsaturated polymerizable water-soluble nonionic surfactants formed by the reaction of a diallylamine compound with ethylene oxide, propylene oxide or butylene oxide, in emulsion polymerization reactions. Similarly, U.S. Pat. No. 5,162,475 (incorporated herein by reference) provides alpha, beta-ethylenically unsaturated poly(alkylenoxy) polymerizble surface active compounds for use in emulsion polymerization. For additional examples of polymerizble surfactants for use in emulsion polymerization processes, see U.S. Pat. Nos. 4,377,185 and 4,049,608. Also see WO 89/12618, EP 747456 A2, and EP 770655 A2; all describing various approaches utilizing ethylenically unsaturated surfactant to produce CASE materials with reactive surfactants.
Non-polymerizble surfactant techniques to overcome the traditional problems encountered in performing an emulsion polymerization process are numerous. U.S. Pat. No. 3,941,857 describes the use of epoxy resins that react with the residual anionic, cationic or nonionic surfactant. Polymerizble compounds such as allyl alcohol (and esters thereof) have been found to be ineffective due to the formation of undesirable high levels of coagulum in the final emulsion polymerization product. Additionally, see U.S. Pat. Nos. 4,224,455; 5,399,617; 4,075,411; 5,344,867; 5,296,627; 5,679,732, 5,536,811; 4,912,157; and 5,039,339; and WO 97/45495.
Thus, there is a need for emulsion polymerization latexes comprising polymers and discrete polymeric particles that are well suited for use in CASE applications, as well as a need for processes to prepare such latexes. There is a specific need for CASE materials which comprise polymer latexes, wherein the final CASE materials possess low water sensitivity, improved scrub resistance and/or improved adhesion properties. Additionally, improved CASE materials with increased latex shear stability and lowered film yellowing tendencies are highly desirable.